The meso-structure of rock influences its macro-mechanical properties. In traditional digital image processing, the filter operator causes fuzzy edges. There is a lack of image processing methods which can conveniently, and quickly, obtain a continuous, smooth, and closed curve with a clear boundary. In this study, a Chan-Vese (C-V) module of the partial differential equation (PDE) method was used to realise the three-phase segmentation of granite. Then, the AUTOLISP language was adopted to allow automatic line connection of the discrete boundary points in the digital image. The meso-scale model was implemented into numerical calculations to explore the evolution of a meso-crack. The crack originated from the stress concentration resulting from the uncoordinated deformation of the non-homogeneous materials under a Brazilian splitting test. The crack first appeared inside the materials with weak mechanical properties along the main diagonal of specimens under uniaxial compression. A stress concentration first appeared on the quartz-mica contact surface under triaxial compression. The tensile stress enveloped the weaker mica and feldspar as the load increased.

岩石的细观结构影响其宏观力学性能。在传统的数字图像处理中，滤波运算符会导致模糊边缘。缺乏能够方便，快速地获得具有清晰边界的连续，平滑和闭合曲线的图像处理方法。在这项研究中，使用偏微分方程（PDE）方法的Chan-Vese（CV）模块来实现花岗岩的三相分段。然后，采用AUTOLISP语言来允许数字图像中离散边界点的自动线连接。将中尺度模型应用到数值计算中，以探索中裂的演变。裂纹起因于在巴西劈裂试验中非均质材料不协调变形引起的应力集中。在单轴压缩下，裂纹首先出现在材料内部，其机械特性沿试样的主要对角线变弱。在三轴压缩下，应力集中首先出现在石英-云母接触表面上。随着载荷的增加，拉应力包围了较弱的云母和长石。